Infection [INF] is a gamemode in which the survivors must avoid taking damage of any kind, whether it be damage from a zombie to taking fall damage. After you have been damaged, the virus side bar (from the Anti-VirusObjective) will show up to the right side of your screen. To cure yourself, you will need to use a healing item. It takes 1-3 minutes to reach 100% meaning you need to heal within that time otherwise you will die.
Tips
Using Pills will only reset the bar as after the initial full health, your health will decrease meaning you "take" damage.
Using a health vest is very buggy here as the game will think you have taken initial damage at the start of the game meaning you need a healing item 1 minute into the round.
Using the Golden Ribbon is even more glitchy, as after you have healed 100% your virus bar will not go away, causing death.
Bringing healing items (such as the Candycane or Medkit) is recommended as the supply boxes won't always give you healing items.
Self harming will still trigger the virus bar.
Trivia
This is the least common gamemode out of the "common" gameplay gamemodes.
Because of this, this is one of the least favored gamemodes in R2D.
This can be considered the R2D form of what is now Rapid Infection in R2DA, with different mechanics.